Wells are generally drilled into the ground or ocean bed to recover natural deposits of oil and gas, as well as other desirable materials that are trapped in geological formations in the Earth's crust. Wells are typically drilled using a drill bit attached to the lower end of a “drill string.” Drilling fluid, or mud, is typically pumped down through the drill string to the drill bit. The drilling fluid lubricates and cools the bit, and may additionally carry drill cuttings from the wellbore back to the surface.
In various oil and gas exploration operations, it may be beneficial to have information about the subsurface formations that are penetrated by a wellbore. For example, certain formation evaluation schemes include measurement and analysis of the formation pressure and permeability. Other measurements may include extracting fluid from the formation, and analyzing and/or testing samples of formation fluid. These measurements may be useful for predicting the production capacity and production lifetime of the subsurface formation.
Accordingly, a representative and/or accurate sample of the formation fluids may be desired. However, in the process of drilling, the drilling fluid may seep and/or permeate through the wellbore walls. In this event, the drilling fluid may contaminate a formation fluid near the wellbore wall. In order to obtain a representative and/or accurate sample of formation fluid, sufficient fluid may need to be pumped from the formation such that the amount of drilling fluid and/or contaminants in the pumped fluid may be reduced and a representative and/or accurate sample may be captured. After the contamination by drilling fluids is reduced, appropriate testing and/or analysis may be conducted on the fluid sample.